If the traditional wall between licensed and unlicensed spectrum is starting to crumble in the 4G era, it will come under impossible strain with the far broader demands of 5G. Preston Marshall, technical program manager for spectrum at Google Access, told the recent 5G North America conference: “We have to break the model of exclusive spectrum.” He believes the shared spectrum elements of the FCC’s new CBRS (Citizens’ Broadband Radio Service) in 3.5 GHz provide a good template for how 5G spectrum could be used more flexibly, and services deployed more quickly. This would avoid the perennial problem of expensive spectrum lying unused because carriers do not find the financing to build out the networks as well as purchase the…